In traditional capacity planning methods, there is usually little spare capacity left in the network after each capacity planning horizon is executed. This is due to the fact that spare capacity shows up simply as cost and costs are being minimized in traditional capacity planning methods. Therefore, a network could run out of capacity in places soon after the current planning time horizon is over. This further leads to the needs to augment many of the network links in the very near future. Thus, such capacity planning method can minimize the current cost but at the expense of incurring a larger cost in the near future. In order to minimize the current cost, these methods end up proposing long routes for many of the circuits, e.g., a shorter route is not available because one of the required links does not have the necessary capacity. However, since additional capacity will eventually be added on all the links, these circuits with unnecessarily long routes will then show up as misrouted circuits and will need to be re-groomed. This involves extra operations cost as well as a hit, a brief service interruption, to the circuit. Furthermore, it also requires getting a customer's permission before a circuit can be re-groomed, which is a very time-consuming manual process.
To avoid the aforementioned shortcomings in the traditional capacity planning methods, the network must maintain an appropriate amount of spare on each link as it takes a fairly long lead-time to order new capacity and capacity is deployed in relatively large chunks. Therefore, a need exists for a method and apparatus for capacity planning with proper accounting of spare capacity within a network.